In reply to Sanmei.

I think you are trying to create a sliced fit plot. You must specify the value of the covariates (for example, AGE, SEX, BMI, etc.) at some location, such as their mean value or reference value. You then should score the model at those values for a range of values for the raw_T_fish variable. For the main idea, see the article "Visualize multivariate regression models by slicing continuous variables."